PDA

View Full Version : Op amp current supply


m718
Aug8-09, 07:34 PM
Do opamps have current limit, I have an OP-27 dual supply connected to 2 9V batters the battery measures 3 Amps and 16 volts is this too much current?

berkeman
Aug8-09, 10:49 PM
Do opamps have current limit, I have an OP-27 dual supply connected to 2 9V batters the battery measures 3 Amps and 16 volts is this too much current?

There is some circuit problem. The OP27 is a standard opamp, so it will not draw or drive currents much over a few 10's of milliamps.

http://www.analog.com/en/other/militaryaerospace/op27/products/product.html

Check the power connections (maybe the +/- supplie connections are reversed?). Also, be careful to take usual ESD/handling precautions, as touching a powered-up exposed circuit can cause latchup.

When you power up your circuit (assuming the 9V batteries aren't dead by now), what gets hot?

m718
Aug8-09, 10:52 PM
There is some circuit problem. The OP27 is a standard opamp, so it will not draw or drive currents much over a few 10's of milliamps.

http://www.analog.com/en/other/militaryaerospace/op27/products/product.html

Check the power connections (maybe the +/- supplie connections are reversed?). Also, be careful to take usual ESD/handling precautions, as touching a powered-up exposed circuit can cause latchup.

When you power up your circuit (assuming the 9V batteries aren't dead by now), what gets hot?

resistors I put on the + supply got hot anything less than 10k just burned

berkeman
Aug8-09, 10:54 PM
Can you post your schematic? Something in the middle must be hooked up wrong. If you do not load the opamp, are the currents small?

m718
Aug8-09, 11:19 PM
Can you post your schematic? Something in the middle must be hooked up wrong. If you do not load the opamp, are the currents small?

Its a very simple 2 opamp circuit so it must be the op amps I will replace them.

m718
Aug8-09, 11:24 PM
But my opamps were brand new, when I connect the batteries to the opamp circuit I connect the ground first then + then -, is this ok or is it damaging the amps?

berkeman
Aug9-09, 12:18 AM
But my opamps were brand new, when I connect the batteries to the opamp circuit I connect the ground first then + then -, is this ok or is it damaging the amps?

Not sure without a schematic. Generally you should use a DPDT switch to connect both of the rails at the same time.

Mike_In_Plano
Aug9-09, 01:38 AM
Sounds like it's mis-wired. It's easy to run high currents through the device's substrate. For example, just reversing the power supply connections will draw a huge current, while only dropping about .6-1 volt.

-Mike